The present invention relates to a lens barrel such that a plurality of lens groups are collapsed and stored in one state, and are moved to predetermined positions and used in another state. In particular, the present invention relates to a lens barrel unit suitable for a zoom lens where a focal length is changed by relatively moving a plurality of lens groups, and to an imaging apparatus such as a camera using the lens barrel unit as described above.
With an enhanced performance of a photographing lens such as a zoom lens which is capable of changing a focal length and a development such as miniaturizing in response to a user's request, use of an imaging apparatus such as a digital camera using a so-called collapsible-type photographing lens in which at least a part of a lens barrel is stored inside a body of the imaging apparatus except when photographing has been increased. Moreover, due to not only a request for a simple miniaturization but also a request for a further decrease in thickness, it has been becoming more important to maximally decrease a thickness of a lens barrel part in a collapsed and stored state.
As a technique in response to a request for thinning an imaging apparatus as mentioned above, a structure having a collapsed-type structure such that at least a part of a lens barrel is stored inside a body of the imaging apparatus except when photographing and a part of the lens groups is retracted and moved from a photographic optical axis when the lens barrel is collapsed and stored is used. The technique above is disclosed in Japanese patent application publication numbers 2006-330657 and 2008-90201, for example.
The structure disclosed in Japanese patent application publication number 2006-330657 makes it possible to decrease a size in an optical axis direction of a whole lens group and a thickness of a whole imaging apparatus, because a part of the lens groups is retracted from the photographic optical axis when the lens barrel is stored. Incidentally, in this case, a retraction lens group which is retracted from the optical axis performs a retraction movement and a movement in the optical axis direction on a guide shaft extending only up to a thickness of the lens barrel, therefore a maximum moving range of the retracting lens group is determined by the thickness of the lens barrel. And therefore it is necessary to increase a moving range of the lens in order to achieve a zoom lens with a higher variable magnification.
In a case of the above technique disclosed in Japanese patent application publication number 2006-330657, in order to increase a moving range of a retraction lens group, it is necessary to increase a thickness of a lens barrel. Therefore, it is difficult to decrease a thickness without changing a variable magnification.
On the other hand, Japanese patent application publication number 2008-90201 discloses a structure which moves a retraction lens frame including two parts of a holding cylinder part which holds a lens group movably in the optical axis direction, and a lever part which moves the holding cylinder part to move the lens group in the optical axis direction. In particular, structures disclosed as embodiments 3 and 4 of Japanese patent application publication number 2008-90201 make it possible to increase a maximum moving range of a third lens group serving as a retraction lens by a simple structure.
In the structures disclosed in Japanese patent application publication number 2008-90201, one end part of a lever which pushes out the lens group contacts a fixed cylinder when moving maximally, so that the lever rotates and the maximum moving range is ensured. In the method above, a movement of the retraction lens group is performed in a photographing range, so that a position in the optical axis direction of the retraction lens largely depends on a rotation angle of the lever and a variability of a contact position. A position deviation in the optical axis direction that displaces an image forming position causes an out-of-focus condition. In addition, the lever rotates in a vicinity of a maximum moving position in the optical axis direction of the retraction lens group, and this position is a position where a biasing force of a compression torsion spring in the optical axis direction which biases the retraction lens group is approximately maximum. In this position, if a rotation force to further rotate the lever is added, a drive force which is necessary for the movement in the optical axis direction of the retraction lens group is further increased.